US3155062A - Joining cord ends - Google Patents

Description

Nov. 3, 1964 H. WESTMIJZE ETAL JOINING CORD ENDS Filed Nov. 15, 1962 3,155,062 HWING QGRD ENDS Herman Westmijze, Velp, and Leendert Ploegen', arnhem, Netherlands, assigner-s to NN. nderzoekingsinstituut Research, Arnhem, Netheriands, a corporation of the Netherlands Filed Nov. l5, i952, Ser. No. 238,33@ Claims priority, application Netherlands Nov. 30, 1961 3 Claims. (Cl. i12-412) The invention relates to the joining of cord ends in such a manner that two cord ends are laid side by side in opposite directions and are joined together by means of a zig-zagged seam. The invention also relates to cords comprising such joints, to cord fabrics comprising such cords, and to products consisting entirely or partly of such cords or cord fabrics.

By cords are also to be understood hereinafter all those products which are to be regarded as cords in the most extended sense of the word. This includes in particular cords used to reinforce the canvas of driving belts, motor car tires, and like products, but it also comprises trimming cords, tying cords, cables, etc. Moreover, the cords may vary widely as far as their chemical compositions are concerned, including natural animal and vegetable bers such as cotton, linen and the like, as well as synthetic fibers of which the rayons, nylons and polyolenes may be considered representative.

Particularly in cases Where the cords are used as reinforcement the cord joints are to meet very 'exacting requirements. In this connection much has been done already for the improvement of joints.

Heretofore such edorts were largely directed to using different knot patterns for tying the cord ends together. 'Ihe most widely varying knots were used, but they all showed great drawbacks. The main drawback is the high loss of strength of a knot relative to the cord. Generally, the strength of cord knots is not more than 60% of the cord strength.

It follows then, when the cords so joined are used in further processes the knots may break or come undone and that in a product made of this cord there may be latent weak spots. These weak spots are particularly undesirable if the cords are incorporated in products subject to considerable stress such as motor car tires or driving belt canvas.

An additional disadvantage to joining cords by means of knots consists in that at the knot there are practically always projecting loose filaments or cord ends. These may give rise to entanglements between the various cords or to the cords getting caught on the after-processing machines.

More recently it has been proposed to solve the problem by joining the two cord ends, which are laid side by side and in opposite directions, by means of a Zigzagged seam. This method has great advantages over knotting as the strength of the joint when loaded for a short time is 90% of that of the cord. Moreover, this joint is initially free from projecting cord ends. An additional and also very important practical advantage is that this method can be carried out more rapidly than the knotting, it being possible for the joints to be made by means of an appropriate sewing machine, which is not nearly so monotonous or tiring as knotting.

In spite of these advantages, this method still has serious drawbacks in actual practice. Although a joint strength equal to 90% of the cord strength represents a considerable improvement over the'strength of a knotted joint, it has been found in practice that the joints should be still stronger.

For example, this 90% strength of the sewed joints cannot be maintained if a cord joined in this way is kept States Patent O i 3,155,%Z Patented Nov. 3, 1964 ice under tension for a relatively long time in the subsequent processing or use.

The after-process may, for instance, consist in additional stretching of the cord or in impregnating it while keeping it under tension, and the subsequent drying of the cord thus treated.

The decrease in strength is due to the fact that the tension is largest at the extreme ends of the joints. The extreme or end stitches, which are weak by nature, may then come loose or break, upon which the tension at the next, adjoining stitches is highest. This process continues and the length of the zig-zagged seam becomes smaller and smaller so that the strength of the joint gradually declines. After some time, the length of the seam is reduced to a minimum and the seam will then ,break spontaneously along its entire length. The fact that the seam gradually loosens moreover causes the formation of loose projecting cord ends. This is attended with the above-described undesirable effects'.

We have found, however, that all the aforementioned drawbacks may be avoided if the cord ends are joined by our improved method as hereinafter described.

It is an object of the present invention to provide an improved method for joining two cords.

Another object is to provide a method whereby two cords may be joined readily by an improved seam using semiautomatic means such as a sewing machine.

A further object of the invention is the provision of an improved joint seam of relatively simple construction having a strength at least equal to that of the cords themselves.

Still another object is the provision of a seam for joining two cords in which the stitches forming said seam are so arranged that tensional force applied to the joint is distributed substantially uniformly among the stitches forming the seam.

These and other objects will become readily apparent to those skilled in the art from the accompanying drawings and the following description.

The present invention consists in that the joining is carried out with the two cord ends laid side by side and in opposite directions and the ends sewn together by means of a zig-zagged seam, said seam changes at its ends into a looped seam such that the stitches are wound around one of the cords and pulled through the other cord.

lf the cords are joined in this way, they do not tend to come loose or to break at the ends. Moreover, the strength of the joint can in practically all cases be maintaned at more than of the cord strength, even when the cord is loaded under tension for a relatively long time.

This result may be explained as follows:

If two pieces of cord, which are joined so that their free ends are laid side by side, are subjected to a tensional force, there will prevail no tension at the extremities of the two free ends, and the pieces of cord against the free end will be subjected to the full tensional force. Consequently, in these places the states of elongation in the two pieces of cord will be extremely different. As a result, the tendency of the cord pieces to shift relative to each other is strongest at their ends, so that with the ordinary zig-zagged seam the tension is highest in those places. This' results in the progressive failure of the stitches described above.

By drawing the stitches at the ends only through one of the pieces of cord, according to the invention, there remains in principle some freedom of movement between said cord ends. When the joint thus made is subjected to some force, the wrapped piece of cord is to some eX- tent free to move through the wrapping. As a result of the friction between the adjacent cord ends, the load on the one piece of cord will gradually decrease toward its free end, and the load on the other piece of cord will gradually increase from its free end, and the seam joining the two cord ends will be loaded substantially uniformly along its entire length.

The looped seams may be made in two Ways, namely such that the free ends of the cord sections are encircled or such that the stitches are pulled through the free ends.

It has been found that the joint can be made strongest according to the invention if the stitches `are pulled through the free ends of the cord sections. When the joint is subjected to tensional force, the mechanical load to which thesey free ends are subject is smallest at the looped seam, Vso that these free ends are apparently the most capable of standing up to any weakening as a result of stitching.

A joint thus made is capable of withstanding a tensile load which is at least as high as that of the cord. 'I he strength does not decline when the joint is loaded for a long time.

It is preferred that the stitches of the looped seam are spaced at closer intervals than the stitches of the zigzagged seam.

This makes it possible for the overall length of the searn to be smaller without the looped seams being additionally weakened by the stitch punctures. For these stitch punctures are in the cord ends which are subject to little or no tension, whereas the actual Zig-zagged seam must along its entire length transfer the entire tensional force' to cord sections which are weakened little as possible by stitch punctures.

lt has been found that a satisfactory joint of minimum length can be obtained if the zig-zagged searn comprises at least zig-zag stitches and the looped seam at least zig-zag stitches, and if the length of the zig-zagged seam is at least times the thickness of the cord, and the length of the looped seams is at least 12 times the thickness of the cord.

In addition to its application to a method of joining the cord ends, the invention also relates to the cords which are joined in this manner, and to cord fabrics comprising such cords, and to products consisting entirely or partly of these cords or cord fabrics. The cords and cord fabrics made according to the invention have been found of particular value if the cords are used for the purpose of reinforcing motor car tires or driving belts, the cord fabric forming the canvas of these tires or belts. The motor car tires and the belts thus man factured are less likely to be subject to canvas ruptures.

For the purpose of explaining the invention there now follows a description, with reference to a drawing, of a representative cord joint, the invention, of course, not being limited to this single example. Many other specic cord joints, and other types of cord are within the purview of this invention` Referring now to the drawings, in FIGURE 1 there are shown two cords, l and 2. ln this example, the cords have a thickness of 0.85 mm. each and are each made up of two strands of multilament rayon yarn. Each of these strands has a thickness of 1650 denier. They are obtained by wet-spinning viscose into an acid spinning bath.

The cords 1 and 2 are laid side by side with their ends, along a distance of 7 cm., along which distance the ends are sewn together' by means of threads 3, use being made of a suitable sewing machine.

The seam is divided into two looped seam sections a and c and one zig-zagged seam section b, intermediate sections a and c.

The looped seam sections a and c each have a length of 1.5 cm, and each consist of 30 zig-zag stitches.

The zig-zaggcd seam section is 4 crn. along and consists of 20 zig-zag stitches.

The looped seam section a is made so that the stitches are pulled through the end of cord 2 and overcast around the cord 1 as shown in more detail in FIGURE 2, an enlarged View of the cords and seam along line 2 2 of FIGURE 1.

Similarly, the stitches of the looped seam section c are drawn through the end of the cord l and wound around the cord 2, as shown in more detail in FIGURE 4.

The zig-zagged seam section b is made so that all the stitches are drawn through 4the centres of both cord 1 and cord 2 as shown in more detail in FIGURE 3, an enlarged view of the two cords and the seam along the line 3 3.

Joining the cords in the above-described manner may be carried out for example, on those types of sewing machines which sew various patterns and designs by using exchangeable pattern disks in the sewing machine.

The pattern disks serve to regulate the sewing machine as follows:

l) while the adjacent cord ends are being fed through the machine a constant stitch interval of 0.5 mm. must be maintained along a distance (section a)=1.5 cm.,

subsequently a cons-tant interval of 2 mm. along a distance of (section b)=4 cm., and finally again a constant interval of 0.5 mm. along a distance (section c)=1.5 cm.;

(2) during this transport the stitch width must successively change along the three aforementioned sections, ie. from about 1.5 rnrn., in section a, to 0.85 mm. in section b and back to 1.5 mm. in section c;

(3) also during this transport along the aforementioned sections a, b and c, the path of lthe cords andthe mean position of the stitching needle must at the two points of transition be displaced 0.25 mm. relative to each other.

For the-se purposes three pattern disks may be placed in the sewing machine. For instance use can be made of a sewing machine which is obtainable under the trademark Necchh type Super Nova Julia, automatic 534.

it will be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

W hat is claimed is:

1. A cord fabric comprising a pair of cord ends laid parallel in opposing directions and a stitched seam joining said ends, said seam being formed of a first section on which the stitches are looped about one of said cords and penetrate the body of said other cord, a second section of zig-zag stitches penetrating both cords, and a third' section in which the stitches are looped about one of said cords and penetrate the body of the other said cord. Y

2. A cord fabric according to claim 1 in which the stitches of the rst and third seam sections are looped `about different cord ends.

3. A cord fabric according to claim 2 in which the length of the rst and third sections of the seam is at least twelve times the diameter of a cord end and the length of the second section of the seam is at least thirtytive times said diameter.

References Cited in the le of this patent UNITED STATES PATENTS 2,126,254

Claims (1)

1. A CORD FABRIC COMPRISING A PAIR OF CORD ENDS LAID PARALLEL IN OPPOSING DIRECTIONS AND A STITCHED SEAM JOINING SAID ENDS, SAID SEAM BEING FORMED OF A FIRST SECTION ON WHICH THE STITCHES ARE LOOPED ABOUT ONE OF SAID CORDS AND PENETRATE THE BODY OF SAID OTHER CORD, A SECOND SECTION OF ZIG-ZAG STITCHES PENETRATING BOTH CORDS, AND A THIRD SECTION IN WHICH THE STITCHES ARE LOOPED ABOUT ONE OF SAID CORDS AND PENETRATE THE BODY OF THE OTHER SAID CORD.

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